Methods and apparatus for providing ventilation to a patient

ABSTRACT

The present technology relates to methods and apparatus to provide ventilation to patients. In particular, the present technology relates to changing ventilator parameters to match changing patient metabolic demand.

1. CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority to AustralianProvisional Patent Applications AU 2011904599 filed 7 Nov. 2011, AU2012902501 filed 15 Jun. 2012 and AU 2012902693 filed 26 Jun. 2012, theentire contents of each being incorporated herein by reference.

2. BACKGROUND OF THE INVENTION

Field of the Invention

The present technology relates to methods and apparatus for thetreatment and/or amelioration of respiratory disorders. In particular,the present technology relates to methods and apparatus for providingventilation to a patient.

Related Art

The respiratory system of the body facilitates gas exchange. The noseand mouth form the entrance to the airways of a patient.

The airways consist, of a series of branching tubes, which becomenarrower, shorter and more numerous as they penetrate deeper into thelung. The prime function of the lung is gas exchange, allowing oxygen tomove from the air into the venous blood and carbon dioxide to move out.The trachea divides into right and left main bronchi, which furtherdivide eventually into terminal bronchioles. The bronchi make up theconducting airways, and do not take part in gas exchange. Furtherdivisions of the airways lead to the respiratory bronchioles, andeventually to the alveoli. The alveolated region of the lung is wherethe gas exchange takes place, and is referred to as the respiratoryzone. See West, Respiratory Physiology—the essentials.

A range of respiratory disorders exist.

Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a groupof lower airway diseases that have certain characteristics in common.These include increased resistance to air movement, extended expiratoryphase of respiration, and loss of the normal elasticity of the lung.Examples of COPD are emphysema and chronic bronchitis. COPD is caused bychronic tobacco smoking (primary risk factor), occupational exposures,air pollution and genetic factors. Symptoms include: dyspnoea onexertion, chronic cough and sputum production.

Neuromuscular Disease (NMD) is a broad term that encompasses manydiseases and ailments that impair the functioning of the muscles eitherdirectly via intrinsic muscle pathology, or indirectly via nervepathology. Some NMD patients are characterised by progressive muscularimpairment leading to loss of ambulation, being wheelchair-bound,swallowing difficulties, respiratory muscle weakness and, eventually,death from respiratory failure. Neuromuscular disorders can be dividedinto rapidly progressive and slowly progressive: (i) Rapidly progressivedisorders: Characterised by muscle impairment that worsens over monthsand results in death within a few years (e.g. Amyotrophic lateralsclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers);(ii) Variable or slowly progressive disorders: Characterised by muscleimpairment that worsens over years and only mildly reduces lifeexpectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic musculardystrophy). Symptoms of respiratory failure in NMD include: increasinggeneralised weakness, dysphagia, dyspnoea on exertion and at rest,fatigue, sleepiness, morning headache, and difficulties withconcentration and mood changes.

Chest wall disorders are a group of thoracic deformities that result ininefficient coupling between the respiratory muscles and the thoraciccage. The disorders are usually characterised by a restrictive defectand share the potential of long term hypercapnic respiratory failure.Scoliosis and/or kyphoscoliosis may cause severe respiratory failure.Symptoms of respiratory failure include: dyspnoea on exertion,peripheral oedema, orthopnoea, repeated chest infections, morningheadaches, fatigue, poor sleep quality and loss of appetite.

Mechanical ventilators have been used to ameliorate the aboverespiratory disorders.

3. SUMMARY

The present technology relates to providing ventilation and, inparticular, to methods and apparatus for providing ventilation to awakepatients.

The present technology also relates to methods and apparatus providingventilation to sleeping patients.

One aspect of one form of the present technology is a method ofproviding ventilatory support, or ventilatory assistance, to assist apatient to exercise.

One aspect of one form of the present technology is a ventilatorconstructed and arranged to assist a patient to exercise.

Another aspect of one form of the present technology is a ventilatorconstructed and arranged to reduce a ventilatory limitation to exerciseas the result of disease.

An aspect of one form of the present technology is a ventilator that isresponsive the rate of respiration of a patient.

Another aspect of one form of the present technology relates to methodsand apparatus for improving the comfort of awake patients being providedwith non-invasive ventilation.

Another aspect of one form of the present technology relates to methodsand apparatus for changing ventilation parameters of a ventilator tomatch patient metabolic demand, in particular when the metabolic demandis changing. In one form the present technology provides an increase toeither or both of ventilation and ventilatory support as metabolic loadincreases.

Another aspect of one form of the present technology is a ventilatorthat is configurable to move between a plurality of different settingsto assist a patient in an exercise regime, as metabolic demandincreases, and/or as metabolic demand decreases.

One aspect of one form of the present technology is a processorprogrammed to implement one or more algorithms.

Another aspect of one form of the present technology relates to aventilator having a plurality of predefined discrete activity modes orstates and moves manually or automatically between modes or states (e.g.(i) Quiet sitting; (ii) Walking around; (iii) Running). In another form,the ventilator has a predefined continuous support pathway, and moves(manually or automatically) along the pathway in response to demand. Inthis way, an indication of change in metabolic demand and/or lungmechanics is input manually or automatically. Preferably the modes orpathway will have an Expiratory Positive Air Pressure (EPAP) value thatranges from about 4 cmH2O to a limit of about 10 cmH2O. In one form thelimit is a predetermined limit. In other forms, the limit is notpredetermined and is calculated from a measure of intrinsic PEEP. Atthis limit, an additional increase, or further increases in demandpreferably do not give rise to a further increase in EPAP, hence thelevel of expiratory positive air pressure will remain substantiallyconstant. Manual adjustments may be made using a remote control, e.g.with buttons and/or joystick.

Another aspect of the present technology relates to apparatus thatallows a patient to manually trigger a ventilator to deliver a breath.In particular, the present technology may allow a patient to manuallytrigger delivery by the ventilator of an inspiration phase of a breathto the patient.

Another aspect of the present technology relates to apparatus thatallows a patient to manually cycle a ventilator, and thus to manuallycause the device to transition from the inspiratory phase to theexhalation phase. Breaths may be cycled by a mechanical ventilator whena set time has been reached, or when a pre-set flow or percentage of themaximum flow delivered during a breath is reached, depending on thebreath type and the settings. Here, preferably breaths can be manuallycycled upon a manual cycle command given by a patient.

Another aspect of the present technology relates to apparatus thatallows a patient to manually adjust the level of pressure support or thetarget ventilation of a ventilator.

Another aspect of the present technology relates to apparatus thatallows a patient to manually adjust the level of End Expiratory Pressure(EEP) or Expiratory Positive Air Pressure (EPAP) of a ventilator.

Another aspect of one form of the present technology relates to acontroller for a ventilator constructed and arranged to calculate atypical duration of a manually triggered breath or a manually cycledbreath.

Another aspect of one form of the present technology relates to methodsand apparatus that, in a first mode, allow a patient to manually controlone or more of the following features; triggering, cycling, the level ofpressure support, EEP, or EPAP and the level of target ventilation. In asecond mode, the apparatus may provide one or more of automatictriggering, cycling or automatically adjusting the level of pressuresupport, EEP, or EPAP and the level of target ventilation. In someinstances, the automatic adjustments may be based, at least in part, ondata obtained from the manual triggering, cycling, target ventilationand/or pressure support level established by the patient.

According to one form of the present technology, a portable batterypowered ventilator is provided. In one form the ventilator comprises oneor more manual controls constructed and arranged to allow the patient toadjust a ventilator setting between different modes or states, with atleast some states being associated with different activity or exerciselevels. Alternatively or additionally, the ventilator is constructed andarranged to automatically adjust to different activity or exerciselevels of the patient.

In one form of the present technology, a controller for a ventilator isprovided, the ventilator being configured to deliver a pressure supportwaveform to a patient, said pressure support waveform having aninspiratory phase and a subsequent expiratory phase, and the controllerbeing configured to trigger adjustment of at least one parameter of theventilator in response to indication of a change in metabolic demandand/or lung mechanics of the patient.

In one form, a controller is programmed so that a magnitude of change tothe pressure during the expiratory phase is equal to about one third ofa magnitude of change during the inspiratory phase.

Preferably the controller is further configured to accept a signal froma metabolic demand responsive transducer, and to determine a state ofmetabolic demand from said metabolic demand responsive transducer. Ametabolic demand responsive transducer may be one or more of anoximeter, a flow sensor and an electromyograph, e.g. a diaphragmelectromyograph.

The following further aspects are preferred forms of the presenttechnology.

1. A controller for a ventilator configured to allow a patient tomanually, trigger a breath.

2. A controller for a ventilator configured, preferably according to anyone of the previous aspects, to allow a patient to manually cycle abreath.

3. A controller for a ventilator, preferably according to any one of theprevious aspects, constructed and arranged to calculate a typicalduration of a manually triggered breath.

4. A controller for a ventilator, preferably according to any one of theprevious aspects, constructed and arranged to calculate a typicalduration of a manually cycled breath.

5. A controller for a ventilator, preferably according to any one of theprevious aspects, constructed and arranged to automatically trigger todeliver a first breath and to trigger to deliver a subsequent breathafter the elapse of a time duration calculated from a duration of atleast one manually triggered breath.6. A controller for a ventilator, preferably according to any one of theprevious aspects, constructed and arranged to automatically cycle tostop delivery of a first breath and to cycle to stop delivery of asubsequent breath after the elapse of a time duration calculated from aduration of at least one manually cycled breath.7. A controller for a ventilator, preferably according to any one of theprevious aspects, the controller being configured to allow a patient tomanually adjust at least one of the following; a target pressuresupport, a target ventilation level, IPAP, EPAP, a backup rate, Ti min.and Ti max.8. A controller, preferably according to any one of the previousaspects, configured to change one of IPAP or EPAP, in response of achange in the other one.9. The controller of aspect 8, wherein the change in the respective oneof the IPAP and EPAP, the change being a response to a change in theother one, is based on a predetermined function.10. A controller for a ventilator, preferably according to any one ofthe previous aspects, the controller being configured to; receivesignals indicative of level of movement of the patient; and in responseto the indicated level of movement, automatically adjust at least one ofthe following; a target pressure support, a target ventilation level,IPAP, EPAP, a backup rate, Ti min. and Ti max provided to the patient.11. A controller for a ventilator, preferably according to any one ofthe previous aspects, the controller being configured to; receivesignals indicative of the speed of movement of the patient; and inresponse to the indicated speed, automatically adjust at least one ofthe following; a target pressure support, a target ventilation level,IPAP, EPAP, a backup rate, Ti min. and Ti max provided to the patient.12. A controller for a ventilator, preferably according to any one ofthe previous aspects, the controller being configured to; receivesignals indicative of heart rate of respiration rate of the patient; andin response to the indicated heart rate of respiration rate,automatically adjust at least one of the following; a target pressuresupport, a target ventilation level, IPAP, EPAP, a backup rate, Ti min.and Ti max provided to the patient.13. A ventilator comprising the controller of any one of the precedingaspects.14. The ventilator of aspect 13, the ventilator further comprising amanual controller in communication with the ventilator controller, themanual controller being configured to initiate a manual adjustment of atleast one of the following; a target pressure support, a targetventilation level, IPAP, EPAP, a backup rate, Ti min. and Ti maxprovided to the patient.15. A ventilator, preferably according to any one of the previousaspects, constructed and arranged to be adaptable to changing patientmetabolic demand.

4 BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows apparatus including a push-button, a personal computer anda ventilator in accordance with an aspect of the present technology.

FIGS. 2a and 2b show graphs of pressure (y-axis) provided to a patient,versus time (x-axis) in accordance with an aspect of the presenttechnology and a window in which manual triggering is available. FIG. 2ashows an arbitrary triggering window during an EPAP phase (e.g. anexpiratory pressure phase in a pressure waveform provided by aventilator), in which the patient is free to manually trigger a breath,but in this case, does not manually trigger within the window. In theillustrated form, the window is about 1 second long, although in otherforms it may be of a different size. By way of contrast, in FIG. 2b ,the patient has initiated early manual triggering.

FIGS. 3a and 3b shows a graph of pressure (y-axis) versus time (x-axis)in accordance with an aspect of the present technology in which manualcycling is available. FIG. 3a shows an arbitrary cycling window duringan Inspiratory Positive Airway Pressure (IPAP) phase in which thepatient is free to manually cycle the ventilator, but in this case, thepatient does not manually cycle the ventilator. In the illustrated form,the window is about 1.8 second long, although in other forms it may be adifferent size. By way of contrast, in FIG. 3b , the patient hasinitiated early manual cycling.

FIG. 4 shows a schematic of flow versus time for a spontaneouslybreathing patient exhibited through inspiration and expiration cycles ofa breathing cycle. A detail of a portion of the breath is shown in FIG.5.

FIG. 5 shows a detail of FIG. 4. In particular, the Figure shows aportion of a breath with two time points, namely the point in time whena button trigger was manually activated (“button trigger”) and the timepoint when the ventilator would have automatically triggered as flowwould have exceeded a trigger flow point, (“Standard trigger flow”).

FIG. 6 illustrates over time pressure, and activation status of atrigger button and a cruise-control button.

FIGS. 7A and 7B show exemplary options of a pathway in accordance withone aspect of the present technology. The X-axis is metabolic demand,and the Y-axis is pressure. In FIGS. 7A and 7B, two lines are shown, anEPAP line, and an IPAP line. The level of pressure support at a givenlevel of metabolic demand is the difference between the two lines. Asthe level of metabolic demand increases; both EPAP and IPAP mayincrease, e.g. at different rates. Hence the level of support mayincrease from about 7 cmH2O when demand is low, to about 15 cmH2O whendemand is high. An EPAPmax limit is defined. As metabolic demandincreases, EPAP may increase to a maximum level of EPAPmax, and afurther increase in metabolic demand may give rise to a further increasein IPAP, but not to EPAP. The value of EPAPmax may vary from patient topatient. In one form EPAPmax is about 10 cmH2O. In FIG. 7A, the EPAP andIPAP lines are reflective of a continuous change in values in responseto changes in demand, however, in an alternative form exemplarily seenin FIG. 7B, there may be discrete changes, hence the lines resemblesteps.

FIG. 8a shows a Positive Airway Pressure (PAP) device in accordance withone form of the present technology.

FIG. 8b shows a schematic diagram of electric components for a PAPdevice in accordance with one form of the present technology.

FIG. 9 shows, in accordance with one form of the present technology, aPAP device connected to a humidifier, providing a supply of air via anair circuit to a patient interface that is being worn by a patient. Asdepicted, the patient may be sitting quietly reading a book prior toexercising.

FIG. 10 shows an alternative form of one aspect of the presenttechnology.

FIG. 11 shows an example flowchart for implementing control of treatmentin some aspects of the present technology.

The patient may move the ventilator between different stages or statesof demand manually, e.g. by pressing buttons on a remote control. Inanother form, the ventilator will automatically detect a change indemand e.g. by monitoring one or more of heart rate, breathing (orrespiratory) rate, and movement.

5. DETAILED DESCRIPTION

Some patients with certain forms of cardio-respiratory disease, forexample COPD or kyphoscoliosis, may benefit from exercise, but find itdifficult to exercise. The use of a ventilator may assist the patient toperform exercise, when the ventilator performs at least some of the workof breathing. Should the patient's level of activity change (andcorresponding metabolic demand), then a set of ventilator parameters(e.g. level of support, timing of breaths) that might have beenappropriate for the first level of activity may be inappropriate for asecond level of activity, for example when a patient is becoming moreactive, or when becoming less active.

According to one aspect of the present technology, an apparatus 10 isprovided as shown in FIG. 1. The apparatus 10 comprises:

A ventilator device 12, for example a Positive Airway Pressure (PAP)ventilator device, further for example a RESMED STELLAR® ventilator;

A user input device or control member, preferably a push-button 14,preferably connectable to other devices such as a personal computer viaa Universal Serial Bus (USB); and

A controller or a Personal Computer (PC) 16 running a manuals triggeringand/or cycling application.

In certain forms of the present technology, the Positive Airway Pressure(PAP) device may be in the form of a device 4000 (see, e.g., FIGS. 8aand 9) that includes an embedded processor 4230 (see, e.g., in FIG. 8b )for executing one or more algorithms that are stored in a memory 4260.This embedded processor 4230 may be provided instead or in addition tothe processor existing in the Personal Computer 16 in apparatus 10. Inthe description hereinbelow where reference is made only to one of thedevices 16, 4230 or 12, 4000 it should be understood that same may beapplicable also to the other device 16, 4230 or 12, 4000 not mentioned.

5.1 SYSTEMS, ALGORITHMS AND PROCESSES

An aspect of the present technology is one or more algorithms 4300 thatmay be executed by a controller 16 or a processor 4230. In theaccompanying figures algorithm 4300 is indicated in FIG. 8b as beingexecuted by processor 4230; however it is to be understood thatalgorithm 4300 may also accordingly be executed by controller 16.

5.1.1 Patient Intervention

5.1.1.1 Triggering and Cycling

In this embodiment, the apparatus 10 is programmed and configured sothat pressing the button 14 down will trigger the ventilator 12 andreleasing the button 14 will cause the ventilator 12 to cycle. Theinventors have found that this configuration of push to trigger andrelease to cycle is easy to use.

In an alternative configuration, there may be different trigger andcycle buttons or different trigger and cycle activators.

In one form, the normal spontaneous triggering and cycling operation isunaffected.

In one form, the successful button-initiated triggering and cycling aresubject to certain timing window limits.

In this form, a digital communication interface 18 of the ventilator,preferably a ResMed STELLAR® ventilator, that allows for remote controlof settings is used, similar to that used in a sleep laboratoryenvironment. A controller, such as a PC application, monitors thepush-button state and sends the appropriate setting changes to theventilator 12; temporarily changing the parameter “Backup Rate” in thecase of triggering and the parameter “TiMax” for cycling.

“Backup Rate”, with units of breaths per minute, is a preferredparameter of the ventilator 12 that establishes the minimum number ofbreaths per minute that the ventilator 12 will deliver, if not otherwisetriggered. This parameter may be used to virtually instantaneouslytrigger a breath. This is so because, if the ventilator 12 is currentlyin expiration, increasing substantially the Backup Rate reduces theduration of the expiration cycle and effectively triggers a subsequentbreath.

“TiMax”, with units of time, is a preferred parameter of the ventilator12 indicative of, the maximum time, from the commencement of a firstbreath, before the ventilator 12 will automatically change toexpiration, if not otherwise cycled. If the ventilator 12 is currentlyin inspiration, then setting the TiMax to be very short can force acycle (from inspiration to expiration) in a manner similar to the way anincreased backup rate forces a trigger.

A particularity of the ventilator 12 preferably used with thistechnology, preferably a ResMed STELLAR ventilator, is that theallowable settings of TiMax may be determined by the current setting ofBackup Rate.

In the embodiments shown in FIGS. 2a, 2b and FIGS. 3a, 3b ; the,preferably STELLAR, ventilator 12 is configured as follows:

For a patient breathing at a nominal 30 breaths per minute (BPM):

Mode: S (i.e. “Spontaneous” mode for detecting a spontaneous breath of apatient)

Backup Rate: 15 BPM

TiMax: 2.0 sec

5.1.1.2 Manual Triggering

The apparatus is further configured so that upon manual activation ofthe trigger button the apparatus implements the following steps:

(i) Set Backup Rate to 60 BPM (this has the side-effect of changing theTiMax to 0.8 sec)

(ii) Wait 15 ms

(iii) Set Backup Rate back to 15 BPM

(iv) Set TiMax back to 2.0 sec

In one form of the present technology, manual triggering of a breath isonly possible during an EPAP phase, and/or during a defined portion ofthe EPAP phase.

However it is noted that in other forms of the present technology, othersettings may be used.

5.1.1.3 Manual Cycling

The apparatus is further configured so that upon manual activation ofthe cycle button the apparatus implements the following steps:

(i) Set Backup Rate to 60 BPM (this allows 0.2<TiMax<0.8)

(ii) Set TiMax to 0.3 sec

(iii) Wait 15 ms

(iv) Set Backup Rate back to 15 BPM

(v) Set TiMax back to 2.0 sec

With reference to FIGS. 2a and 2b , the following exemplary scenariosare illustrated. A patient progresses through one or more breaths (onebeing shown). With the ventilator 12 set to a TiMax of 2 seconds, thenext breath will not be delivered until the elapse of 2 seconds. In theillustrated example (see FIG. 2b ), the patient manually triggers theventilator 12 before the elapse of the 2 seconds, and thereupon the nextbreath will be delivered to the patient. Manually triggering theventilator may be possible in this example within an “arbitrarytriggering window” of 1 second that is indicated in these figures. Anexemplary beginning of a next breath that is early manually triggeredduring this window is indicated in FIG. 2b by a dashed line.

In an embodiment, this is achieved by increasing the backup rate to arate that is much faster than, a normal rate, for example from 15 BPM to60 BPM. At this relatively rapid rate, a new breath (indicatedaccordingly by the dashed line) will be soon delivered. However shortlythereafter, e.g. 15 ms later, the backup rate will be returned to alower level, e.g. a previous lower level of 15 BPM.

With reference to FIGS. 3a and 3b , in the midst of the ventilator 12delivering a breath to the patient, the patient activates manualcycling—for example by releasing a button—whereupon the ventilator 12stops delivering the breath.

In the illustrated embodiment, TiMax is set to e.g. 0.2 sec, a durationthat is soon passed, and therefore the ventilator 12 may stop deliveringthe breath as indicated by the dashed lines in FIG. 3b . Here too thereis an “arbitrary cycling window” during the IPAP phase in which thepatient is able to manually cycle the ventilator. In these figures, thewindow is about 1.8 second long.

Other forms of the present technology do not adjust TiMax or BackupRate, but directly activate triggering and cycling of a ventilator. Inone configuration, the ability of the patient for manual interventionmay be limited by time constraints.

FIG. 4 shows a schematic of a breath on a flow-time curve, provided by aventilator that is set to be in “Spontaneous” mode (i.e. S mode).Inspiration is shown as positive flow and expiration as shown asnegative flow. This figure shows an example breath with a longexhalation portion.

FIG. 5 shows a detail from FIG. 4. The Flow axis includes a “triggerflow” threshold TF, and a prior art ventilator may be configured totrigger or provide support to a breath of a patient when measuredpatient respiratory flow exceeds the “trigger flow” threshold TF. Inaccordance with the present technology, a supporting breath can bedelivered to the patient sooner than would occur in the prior art or inthe pre-settings of the ventilator by the patient, e.g., manually,triggering the breath. In FIG. 5, for example, a patient that feels thatassistance is needed in order to urge or assist him into inspiration maytrigger a supporting breath at an instance indicated by dashed line 20.This may be achieved, as indicated above, by pushing a trigger button.Then, inspiration assistance is provided and inspiration starts. Asseen, this will advance the support that a patient may be provided withby a factor of time indicated in this figure as “trigger advance” TAD.

5.1.1.4 Pressure Support and EPAP

In another form of the present technology (not illustrated), the patientmanually increases the level of pressure support (e.g. the differencebetween an IPAP level and an EPAP level) by activation of a button.

In one form of the present technology, not shown, there is a joystickthat is used to adjust the level of pressure support. The joystick has anatural neutral position. It may be pushed up, and upon release, it willautomatically return to the neutral position. It may also be pusheddown, and upon release, it will automatically return to the neutralposition.

In one form of the present technology, the apparatus is configured sothat once a patient has pushed up and released the joystick, thepressure support will increase by, e.g., 3 cmH2O.

In one form of the present technology, the apparatus is configured sothat once a patient has pushed down and released the joystick, thepressure support will decrease by, e.g., 3 cmH2O.

In alternative forms, the amount of change may be different to 3 cmH2O,for example, 1 cmH2O, 2 cmH2O, 4 cmH2O, 5 cmH2O, or some other amount.

Alternatively, moving the joystick may continuously change the providedpressure support. The patient can then decide to lock the instantaneouspressure support achieved at a particular point, or let it automaticallyreturn to its initial level. The rate of change of the pressure support,whether driven by the patient or during the automatic return to apredefined rate, may also be predetermined, manually adjustable or both.

For example, in a ventilator delivering a pressure waveform having twolevels, namely an inspiratory pressure (IPAP) and an expiratory pressure(PEEP or EPAP), the patient may be able to manually adjust one or bothof IPAP and PEEP or EPAP.

In an, alternate, regardless of whichever of the IPAP and EPAP areadjusted, the other may also change. The change may be associated with apredetermined function. Thus, in response to the patient's manualcontrol inputs, the IPAP and EPAP will change together, according tothis predetermined function relating the change in EPAP with the changein the IPAP.

In one form, the IPAP and EPAP may be approximately related by thefunction:Δ(IPAP)=3×Δ(EPAP),

i.e., the patient increasing the IPAP by 3 cmH2O will automaticallyincrease the EPAP by 1 cmH2O.

It has to also be appreciated that in some instances, instead ofchanging the pressure support, IPAP or EPAP, a patient may manually (orthe ventilator automatically) adjust a respective target ventilationlevel.

Also, whilst any one of a number of ventilation parameters may beindividually adjustable by the patient, it is envisaged that similarfunctionality may be better facilitated by offering various modes ofoperation of the ventilator, each mode having specific set ofventilation parameters. For example, instead of being offered a largenumber of separate parameters for manual adjustment, a patient may beoffered three different modes: “resting”, “gentle exercise” and“moderate exercise”. Each of these modes or states may be associatedwith a specific set of ventilation parameters, such as respiratory rate,pressure support, target ventilation level, EEP, EPAP etc.

In one form, the patient may manually adjust the pressure waveformprovided by the ventilator, by selecting between running values (i.e.non-discrete) or discrete values of metabolic demand appropriate e.g. tothe level of activity or work he is experiencing. Selecting a certainmetabolic demand accordingly sets a corresponding location along thepathway 21, and together with that a level of EPAP; IPAP and pressuresupport. Manual selection of the metabolic demand may be performed bye.g. pressing buttons on a remote control.

5.1.1.5 Tidal Volume

In one form, the ventilator comprises a control that allows a patient toadjust a tidal volume setting of the ventilator.

5.1.1.6 Oxygen

In one form of the present technology, oxygen is delivered to thepatient. In accordance with one form of present technology, a patientmay manually increase or decrease the flow rate of oxygen.

5.1.1.7 Humidification

In one form of the present technology, the patient can adjust a level ofhumidification provided by the ventilator 12 or 4000 by a humidifier5000 (see e.g. FIG. 9 where device 4000 is shown with humidifier 5000).For example the patient may be able to increase or decrease a level ofrelative and/or absolute humidity.

5.1.1.8 Temperature

In one form, the patient can adjust a temperature of air delivered.

5.1.1.9 Waveform

In one form of the present technology, the patient can adjust the shapeof the pressure waveform. For example, the patient may be able to varythe pressure waveform from a more square wave to a more rounded orsmoother waveform. In alternative arrangement, the patient may be ableto select a waveform from a set of predefined waveforms.

5.1.2 Cruise Control

In another form of the present technology, the apparatus 10 isprogrammed and configured to operate in a semi-automatic fashion, e.g.to learn a pattern of manually activated triggers, and/or cycles. Theventilator is able to learn from the patient a setting appropriate tothe current level of activity. In one form a processor, e.g. 4230, isprogrammed to execute one or more algorithms as follows. For example,the patient may manually trigger the ventilator 12 or 4000 a number oftimes over several breaths. The apparatus 10 calculates a patientpreferred period between breaths and then upon activation of a “CRUISECONTROL” mode, delivers breaths at the patient preferred rate.

In one form, the apparatus 10 is programmed and configured, to determinea running average duration between manually triggered breaths. In oneform the apparatus 10 determines a running average duration betweenmanually cycled breaths.

In one form, the apparatus 10 is programmed and configured to store atime, t0, when the manual trigger is first pressed, and also to storethe times, t1, t2, t3 when a new trigger and subsequent triggers arepressed. For example, the times may be stored in an array of time valuest(i), having an array index i by which time values, where i is aninteger, e.g. so that some consecutive time values of t(i) may be found.The differences t1−t0, t2−t1 and t3−t2 are calculated and an average istaken and stored.

In one form, the apparatus 10 is programmed and configured to store atime, c0, when a manual cycle is first activated (e.g. by release of abutton), and also to store the times, c1, c2, c3 when subsequent cyclesare activated. The differences c1−c0, c2−c1 and c3−c2 are calculated andan average is taken and stored.

FIG. 6 illustrates three lines: a pressure waveform delivered by aventilator (top), trigger button signal (middle) and cruise buttonsignal (bottom). When the trigger button is pressed, the ventilatortriggers to deliver a breath at a pressure of IPAP, and when it isreleased, the ventilator cycles to deliver a breath at a pressure ofEPAP. The duration of the first inhalation portion of the breathingcycle is TI1. The duration of the second and third inhalation portionsare TI2 and TI3, respectively. The durations of the first, second andthird exhalation portions are TE1, TE2 and TE3 respectively.

In one form of the present technology, the apparatus 10 calculatesTEcruise, as the average of the last three inhalations, e.g. TI1, TI2and TI3; and furthermore preferably the apparatus 10 calculatesTEcruise, as the average of the last three exhalations, e.g. TE1, TE2and TE3. Preferably the average is calculated as a running average, sothat if the patient continues to manually trigger and cycle, the averagetimes will be updated. In one form, the average may be calculated fromlast “k” recent stored time values of t(i), with “k” being an integernot exceeding “m”, where “m” is a integer between “0” and “n”, thenumber of samples.

Upon activation of the “CRUISE CONTROL” mode by pressing e.g. the“cruise” button, the ventilator 12 will trigger and subsequently cycleat the average cycle time calculated in the averaging step. See FIG. 6,“Cruise Mode On”.

For example, as shown in FIG. 6, when Cruise control is activated, thelast three inhalations are TI4, TI3 and TI2, and the last threeexhalations are TE3, TE2, and TE1.

HenceTIcruise=(TI4+TI3+TI2)/3TEcruise=(TE3+TE2+TE1)/3

In one form of the present technology, output devices 4290 e.g. feedbacklights and/or chimes are included (see FIG. 8b ). When the apparatus 10has sufficient data a light and/or chime at e.g. the ventilator 12 or4000 will be activated to indicate that the ventilator 12 or 4000 isready to go into cruise control mode. See FIG. 6 “Cruise Ready”.

In this way, a patient can adjust a breath length from that which wouldbe delivered but for the patient intervention.

In one form of the present technology, a warning light and/or chime willbe activated if the patient attempts to enter cruise control mode whenthe apparatus 10 is not ready to enter cruise control mode.

In one form of the present technology, an indicator light and/or chimewill be activated if the patient successfully enables cruise controlmode, and remains activated while cruise control mode is in effect.

5.1.3 Response to Changing Metabolic Demand or Lung Mechanics

Another aspect of one form of the present technology is a device that isconstructed and arranged to be able to provide automatically a suitablepressure waveform in response to changing metabolic demand.

Methods and apparatus are provided to determine a suitable pressurewaveform, including the steps of adjusting the level of EPAP, and/orIPAP, and/or pressure support provided to the patient, with pressuresupport being the difference between EPAP and IPAP.

In another form, providing a sufficient pressure waveform can beperformed by following, e.g. at the controller 16, 4230 or ventilator12, 4000, a predefined continuous support pathway for determining therequired pressure waveform for the patient. An example of such acontinuous pathway can be seen indicated as 21 in FIG. 7A. Here, thepathway 21 is illustrated by the hatched area and is defined by an EPAPline and an IPAP line, that respectively bound the pathway from belowand above.

According to the pathway 21 of FIG. 7A, as the level of metabolic demandincreases, e.g. within a first, range of metabolic demand values, thelevels of IPAP and EPAP increase together, for example increasinglinearly, with it until an inflection point, here indicated by ‘dottedline’ 17, is reached. As the level of metabolic demand increases beyondthis line 17, the level of IPAP also increases, preferably however hereat a different rate, optionally lower than before. The EPAP level asseen may be maintained after this point at a constant level, heredefined as EPAPmax, which in one form is about 10 cmH2O. The level ofpressure support in the pathway is accordingly defined for each givenvalue of metabolic demand as the difference between IPAP and EPAP forthat given value. Here, the pressure support at a certain value ofmetabolic demand is indicated by ‘double sided arrow’ 19.

As seen in FIG. 7B, changes in the level of pressure support may alsovary discretely with change in metabolic demand. Here, these discretechanges are obtained by the IPAP and EPAP lines being stepped shaped.The optional lower rate of increase in IPAP level after the inflectionpoint indicated by line 17; is achieved in this pathway by smaller stepsof increase in the IPAP level.

In yet another form, pre-defined discrete levels of work or metabolicdemand of a patient may be defined, and the apparatus 10 or ventilator12, 4000 may be configured to enable automatic selection of (or movementbetween) these discrete levels. Such pre-defined levels may be definedas: (i) Quiet sitting (e.g. when the body is at rest); (ii) Walkingaround (e.g. when the body is at normal average activity); (iii) Running(e.g. when the body is at a high level of activity). And, the level ofe.g. pressure support at each mode can be: (i) Quiet sitting—about 7cmH2O to about 9 cmH2O, more preferably about 7 cmH2O; at mode (ii)Walking around—about 10 cmH2O to about 13 cmH2O, more preferably about11 cmH2O; and at mode (iii) Running—about 14 cmH2O to about 17 cmH2O,more preferably about 15 cmH2O.

Optionally, a form of apparatus 10 may be configured to function withsuch discrete levels of metabolic demand and in addition with thepathway 21. Thus, the dashed lines seen in FIG. 7A indicate the modes(i), (ii) and (iii) of such a form of apparatus 10, and as seenselecting a mode may affect in this form also the level of EPAP and IPAPthat is provided to the patient. For example, moving from mode (i) to(ii) may also increase the levels of EPAP and IPAP in addition topressure support.

5.1.4 Rate Responsive Ventilator

In one form, the pressure waveform provided by the ventilator may beautomatically set by detecting changes in metabolic demand e.g. bymonitoring one or more of heart rate, breathing (or respiratory) rate,and movement, or state of movement. In one form of the presenttechnology a sensor configured to provide a measure of metabolic demand,e.g. heart rate and breathing (or respiratory) rates, provides an inputto a processor. In one form the metabolic demand responsive sensor is anoximeter 4273 used to detect heart rate and/or respiratory rates (see,e.g., oximeter 4273 indicated in FIG. 8b ).

In one form an oximeter 4273 is used to provide a photoplethysmogram(PPG). One or more respiratory parameters are extracted from a PPGsignal using a time-domain, and/or a frequency-domain processing step.For example, wavelet-based analysis may be used.

In one form a value for heart rate variability is determined from asignal from an oximeter 4273. The value of heart rate variability isused to estimate a level of activity of the vagal nerve, and to infer ameasure of metabolic demand.

In one form, in a further processing step, a respiratory parameterextracted from a PPG signal is used, preferably in conjunction with aparameter extracted from a flow sensor, to estimate a respiratory rate,or as an input to a respiratory rate state machine.

A control algorithm monitors the respiratory rate and in response to achange of respiratory rate, or a change in state of a respiratory ratestate machine, adjusts one or more of IPAP and EPAP.

In one example, when the estimated respiratory rate increases, theventilator or PAP device increases the IPAP level. In a further example,when the estimated respiratory rate increases, the ventilator or PAPdevice increases the EPAP level.

In one example, when the estimated respiratory rate decreases, theventilator or PAP device decreases the IPAP level. In a yet furtherexample, when the estimated respiratory rate decreases, the ventilatoror PAP device decreases the EPAP level.

In this way the ventilator is able to respond automatically to therespiratory rate of the patient, and to assist the patient to exercise.

In one form, actigraphy, e.g. accelerometers, are used to detectmovement of the patient. When a patient starts to walk or exercise, thelevel of movement of the patient is detected and used to respectivelyincrease at least one of a respiratory rate (e.g. breaths per minute),and/or level of pressure support and/or target ventilation.

In one form, an exercise machine is connected to the ventilator. When apatient begins to exercise, the movement of the machine provides aninput to the ventilator to alter a rate and or a level of pressuresupport or target ventilation.

In one form, a wearable sensor is used to detect movement of the patientand as an input to control the ventilator. For example, a GlobalPositioning Sensor (GPS) may be used to detect a movement of thepatient. The change in location and the corresponding differences intime may indicate the speed of the patient. The measured speed can beused as an indication of whether and how quickly the patient is moving.Such an indication may then be used to trigger a corresponding change inthe ventilation parameters, such as provided respiratory rate, level ofpressure support or target ventilation level. In one configuration, thesystem may include a lookup table which relates a specific speed with aspecific respiratory rate, pressure support or target ventilation level.A maximum speed limit, i.e. higher than 1 m/s, may be imposed and speedshigher than the speed limit may be ignored, as they may be indicative ofthe patient movement being assisted by a third party or bytransportation means.

In one form, an analogue sensor or controller is used that is configuredto provide a greater level of support the harder it is pressed. Inanother form, an analogue sensor or controller is used to trigger and/orcycle the ventilator.

5.1.5 Determining EPAP

In one form of the present technology, expiratory pressure level (EPAP)is set automatically to a level at or slightly below the intrinsicpositive end expiratory pressure (PEEP), e.g. as determined by reducingor minimising Expiratory Flow Limitation (EFL). The presence of EFL maybe determined using a forced oscillation technique.

In one form the presence of EFL is determined using a technique such asthat described in Peslin et al. (1993) EUR RESPIR J, 6, 772-784,“Respiratory mechanics studied by forced oscillations during artificialventilation”.

In one form the presence of EFL is determined by applying a sinusoidalpressure waveform, e.g. at 5 Hz, 10 Hz and 20 Hz at the entrance to theairways, e.g. using a loudspeaker placed in parallel with theventilator, or by applying an oscillatory pressure waveform signal to ablower under the control of a processor. The airway is modelled as acombination of resistance, compliance and in one form, inertance.Complex impedances in inspiration and expiration are determined.Intrinsic PEEP is determined by adjusting EPAP and finding the lowestvalue of EPAP which reduces the magnitude of the difference between theinspiratory and expiratory values of the imaginary component of compleximpedance to a level close to that seen in normal patients, or findingthe lowest value of EPAP above which a further increase no longer yieldsa significant decrease in this difference.

This step of determining an EPAP level using a forced oscillationtechnique may, be combined with a step of determining a respiratory ratefrom an oximeter 4273 and/or a flow sensor.

5.1.6 Patient Responsive Algorithm

In one form of the present technology, the processor e.g. 4230 isconfigured to execute an algorithm that includes the following steps:

(i) Adjust tidal volume and respiratory rate to maintain minuteventilation at a value between a predetermined minimum minuteventilation and a predetermined maximum minute ventilation;

(ii) Receive a patient initiated synchrony stimulus;

(iii) Determine a minimum target respiratory rate on the basis of apatient initiated synchrony stimulus; and

(iv) Adjust respiratory rate in response to the patient initiatedsynchrony stimulus.

5.2 APPARATUS/DEVICE

In one form of the present technology, a ventilator 12 takes the form ofPAP device 4000.

PAP device 4000 comprises mechanical and pneumatic components 4100,electrical components 4200 and is programmed to execute one or morealgorithms 4300. The PAP device preferably has an external housing 4010,preferably formed in two parts, an upper portion 4012 of the externalhousing 4010, and a lower portion 4014 of the external housing 4010. Inalternative forms, the external housing 4010 may include one or morepanel(s) 4015. Preferably the PAP device 4000 comprises a chassis 4016that supports one or more internal components of the PAP device 4000. Inone form a pneumatic block 4020 is supported by, or formed as part ofthe chassis 4016. The PAP device 4000 may include a handle 4018.

The pneumatic path of the PAP device 4000 preferably comprises an inletair filter 4112, and a pressure device 4140 such as a controllablesource of air at positive pressure (preferably a blower 4142). One ormore pressure sensors 4152 and flow sensors 4154 are included in thepneumatic path.

The preferred pneumatic block 4020 comprises a portion of the pneumaticpath that is located within the external housing 4010.

The PAP device 4000 preferably has an electrical power supply 4210, oneor more input devices 4220, a processor 4230, a pressure devicecontroller 4240, one or more protection safety circuits 4250, memory4260, transducers 4270 and one or more output devices 4290. Electricalcomponents 4200 may be mounted on a single Printed Circuit BoardAssembly (PCBA) 4202. In an alternative form, the PAP device 4000 mayinclude more than one PCBA 4202. See, e.g., a component 4200 and a PCBA4202 indicated in FIG. 8 a.

The PAP device 4000 is connected to a patient 1000 via an air circuit4170 in use, e.g., as indicated in FIG. 9.

5.2.1 Electrical Components

5.2.1.1 Power Supply 4210

In one form of the present technology power supply 4210 is internal ofthe external housing 4010 of the PAP device 4000. In another form of thepresent technology, power supply 4210 is external of the externalhousing 4010 of the PAP device 4000.

In one form of the present technology power supply 4210 provideselectrical power to the PAP device 4000 only. In another form of thepresent technology, power supply 4210 provides electrical power to bothPAP device 4000 and a humidifier 5000.

In one form of the present technology power supply 4210 is a battery.Preferably the battery has at least enough energy to power the PAPdevice 4000 to allow a patient to exercise for a period, e.g. about 1 toabout 2 hours, alternatively the period is about 2 hours to about 4hours.

5.2.1.2 Input Devices 4220

In one form of the present technology, a PAP device 4000 includes one ormore input devices 4220 in the form of buttons, switches or dials toallow a person to interact with the device. The buttons, switches ordials may be physical devices, or software devices accessible via atouch screen. The buttons, switches or dials may, in one form, bephysically connected to the external housing 4010, or may, in anotherform, be in wireless communication with a receiver that is in electricalconnection to a processor 4230.

In one form the input device 4220 may be constructed and arranged toallow a person to select a value and/or a menu option.

5.2.1.3 Processor 4230

In one form of the present technology, a processor 4230 suitable tocontrol a PAP device 4000 is an x86 INTEL processor.

A processor 4230 suitable to control a PAP device 4000 in accordancewith another form of the present technology includes a processor basedon ARM Cortex-M processor from ARM Holdings. For example, an STM32series microcontroller from ST MICROELECTRONICS may be used.

Another processor 4230 suitable to control a PAP device 4000 inaccordance with a further alternative form of the present technologyincludes a member selected from the family ARM9-based 32-bit RISC CPUs.For example, an STR9 series microcontroller from ST MICROELECTRONICS maybe used.

In certain alternative forms of the present technology, a 16-bit RISCCPU may be used as the processor 4230 for the PAP device 4000. Forexample a processor from the MSP430 family of microcontrollers,manufactured by TEXAS INSTRUMENTS, may be used.

The processor 4230 is configured to receive input signal(s) from one ormore transducers 4270, and one or more input devices 4220.

The processor 4230 is configured to provide output signal(s) to one ormore of an output device 4290, and a pressure device controller 4240.

The processor 4230 is configured to implement the one or more algorithmsexpressed as computer programs stored in memory 4260.

5.2.1.3.1 Clock 4232

Preferably PAP device 4000 includes a clock 4232 that is connected toprocessor 4230.

5.2.1.4 Pressure Device Controller 4240

In one form of the present technology, pressure device controller 4240is located within processor 4230.

In one form of the present technology, pressure device controller 4240is a dedicated motor control integrated circuit. For example, in oneform a MC33035 brushless DC motor controller, manufactured by ONSEMI isused.

5.2.1.5 Protection Circuits 4250

Preferably a PAP device 4000 in accordance with the present technologycomprises one or more protection circuits 4250.

One form of protection circuit 4250 in accordance with the presenttechnology is an electrical protection circuit.

One form of protection circuit 4250 in accordance with the presenttechnology is a temperature or pressure safety circuit.

5.2.1.6 Memory 4260

In accordance with one form of the present technology the PAP device4000 includes memory 4260, preferably non-volatile memory. One or moreof the algorithms described above are stored in memory 4260 and executedby processor 4230 in use.

In some forms, memory 4260 may include battery powered static RAM. Insome forms, memory 4260 may include volatile RAM.

Preferably memory 4260 is located on PCBA 4202. Memory 4260 may be inthe form of EEPROM, or NAND flash.

Additionally or alternatively, PAP device 4000 includes removable formof memory 4260, for example a memory card made in accordance with theSecure Digital (SD) standard.

5.2.1.7 Transducers 4270

Transducers may be internal of the device, or external of the PAPdevice. External transducers may be located for example on or form partof the air delivery circuit, e.g. the patient interface. Externaltransducers may be in the form of non contact sensors that transmit ortransfer data to the PAP device.

5.2.1.7.1 Flow 4271

A flow transducer 4271 in accordance with the present technology may bebased on a differential pressure transducer, for example, an SDP600Series differential pressure transducer from SENSIRION. The differentialpressure transducer is in fluid communication with the pneumaticcircuit, with one of each of the pressure transducers connected torespective first and second points in a flow restricting element.

In use, a signal from the flow transducer 4271, is received by theprocessor 4230.

5.2.1.7.2 Pressure 4272

A pressure transducer 4272 in accordance with the present technology islocated in fluid communication with the pneumatic circuit. An example ofa suitable pressure transducer is a sensor from the HONEYWELL ASDXseries. An alternative suitable pressure transducer is a sensor from theNPA Series from GENERAL ELECTRIC.

In use, a signal from the pressure transducer 4272, is received by theprocessor 4230. In one form, the signal from the pressure transducer4272 is filtered prior to being received by the processor 4230.

Processor 4230 uses a signal from the pressure transducer 4272 to assistin control of the pressure delivered to the patient 1000 via patientinterface 3000.

5.2.1.7.3 Oximeter 4273

An oximeter 4273 in accordance with the present technology may be anoximeter from one of the following manufacturers: PHILIPS, MASIMO,NELLCOR. For example, a NELLCOR OxiMax sensor may be used.

5.2.1.7.4 Electromyograph 4274

In one form of the present technology an electromyograph (EMG) 4274 isprovided. The EMG 4274 is configured to monitor activity of thediaphragm of the patient.

5.2.1.8 Output Devices 4290

An output device 4290 in accordance with the present technology may takethe form of one or more of a visual, audio and haptic unit. A visualdisplay 4294 may be a Liquid Crystal Display (LCD) or Light EmittingDiode (LED) display, and a display driver 4292 may be used fordisplaying information on the display 4294.

5.3 ADDITIONAL OR ALTERNATIVE ASPECTS

An example form of a device for implementing one or more of the methodsof the present technology is illustrated in FIG. 10. In some forms, theapparatus 100 may include a patient respiratory interface 102, adelivery tube 110, a controller 104 and a flow generator such as aservo-controlled blower 105.

The patient respiratory interface such as a mask 108 as shown togetherwith the delivery tube 110, provides a respiratory treatment to thepatient's respiratory system via the patient's mouth and/or thepatient's nares. Optionally, the patient respiratory interface may beimplemented with a nasal mask, nose & mouth mask, full-face mask ornasal pillows or tracheostomy tube.

With the flow generator, the apparatus 100 can be configured to generatea respiratory pressure treatment at the patient respiratory interface.To assist this end, the device may further include a pressure sensor106, such as a pressure transducer to measure the pressure generated bythe blower 105 and generate a pressure signal p(t) indicative of themeasurements of pressure. In such a device, the delivery tube 110 mayserve as the sense tube to permit detection of pressure levels suppliedto the mask or patient respiratory interface.

The apparatus 100 may also optionally be equipped with a flow sensor107, which may be coupled with the patient respiratory interface. Theflow sensor generates a signal representative of the patient'srespiratory flow. The signals from the sensors may be used to detectobstructive or central apneas, hypopneas, cardiogenic airflow,respiratory rates and other respiratory related parameters from thesignals measured by the sensors as discussed in more detail herein. Insome forms, flow proximate to the mask 108 or delivery tube 110 may bemeasured using a pneumotachograph and differential pressure transduceror similar device such as one employing a bundle of tubes or ducts toderive a flow signal f(t). Alternatively, a pressure sensor may beimplemented as a flow sensor and a flow signal may be generated based onthe changes in pressure. Although the pressure or flow sensors areillustrated in a housing of the controller 104, they may optionally belocated closer to the patient, such as in the mask 108 or delivery tube110. Other devices for generating a respiratory flow signal or pressuresignal may also be implemented. For example, a motor RPM sensor may beutilized to estimate pressure or flow information supplied by the flowgenerator device based upon the characteristics of the system.

Based on flow f(t) and/or pressure p(t) signals, the controller 104 withone or more processors 114 generates blower control signals. Forexample, the controller may generate a desired pressure set point andservo-control the blower to meet the set point by comparing the setpoint with the measured condition of the pressure sensor. Thus, thecontroller 104 may make controlled changes to the pressure delivered tothe patient interface by the blower. Optionally, such changes topressure may be implemented by controlling an exhaust with a mechanicalrelease valve (not shown) to increase or decrease the exhaust whilemaintaining a relatively constant blower speed.

With such a controller or processor, the apparatus can be used for manydifferent pressure treatment therapies, such as the pressure treatmentsfor sleep disordered breathing, Cheyne-Stokes Respiration, obstructivesleep apnea (e.g., CPAP, APAP, Bi-Level CPAP, AutoVPAP), etc., orcombinations thereof by adjusting a suitable pressure delivery equation.For example, the pressure treatment therapies of the devices describedin U.S. Pat. Nos. 6,532,957, 6,845,773 and 6,951,217, which areincorporated herein by reference in their entireties, may be implementedwith a apparatus 100 of the present technology. For example, asdescribed in these patents, the controller and flow generator may beconfigured to provide pressure support ventilation. Such a treatment mayensure delivery of a specified or substantially specified targetventilation, for example, a minute ventilation, a gross alveolarventilation or a alveolar ventilation, to the patient interface duringthe course of a treatment session by comparing an measure of ventilationwith the target ventilation; or delivery of a tidal volume by comparinga measure of tidal volume with a target tidal volume. Thus, if apatient's respiration causes the measured ventilation to fall below orrise above the target ventilation over time, the flow generator willcompensate with an increase or decrease respectively in the suppliedpressure support ventilation. This may be accomplished with pressurevariations that provide a bi-level form of therapy or some other form oftherapy that may more smoothly replicate changes in a patient'srespiration cycle. While the form of FIG. 10 illustrates a flowgenerator for generating such pressure support ventilation, as describedherein, in some cases a apparatus may be implemented for monitoringwithout a flow generator for a pressure treatment.

Optionally, the apparatus 100 may also include additional diagnosissensors 112 that may be contact or non-contact sensors. For example, thedevice may include an oximeter. The oximeter may generate a signalrepresentative of a blood oxygen level of a patient. A suitable exampleoximeter or monitor device may optionally be any of the devicesdisclosed in International Patent Application No. InternationalApplication No. PCT/AU2005/001543 (Pub. No. WO/2006/037184) orInternational Patent Application No. PCT/AU1996/000218 (Pub. No.WO/1996/032055), the disclosures of which are incorporated herein bycross-reference. As disclosed in these incorporated PCT applications,the monitor may serve as diagnosis sensors that can also optionallyprovide a blood pressure and/or heart or pulse rate monitor formeasuring a heart rate and/or blood pressure of the patient.

In some forms, the diagnosis sensors may also include an ECG monitor.Such a device may be configured to detect cardiac-relatedcharacteristics such as a heart rate and may also determine respiratoryparameters (such as central or obstructive apneas, hypopneas, etc.)Optionally, these parameters may be determined by the analysisalgorithms of controller 104 based on transmission of the ECG data tothe controller or they may be determined by the monitor and betransmitted to the controller 104.

In some forms, the diagnosis sensors may include a movement sensor. Forexample, a suprasternal notch sensor or chest band may be implemented togenerate a movement signal that is indicative of patient effort duringrespiration. Other suitable sensors may include the movement sensingdevices disclosed in International Patent Application No.PCT/AU1998/000358 (Pub. No. WO1998/052467), the disclosure of which isincorporated herein by cross-reference. The movement sensors thus mayprovide a measure of patient effort and/or respiration rate and may beused as an alternative to a flow sensor or in conjunction with otherflow sensors as discussed in more detail herein.

Some forms may monitor respiratory parameters with non-contact infraredor wireless biomotion sensors. One such example is the BiancaMed Dopplerdevice which uses low power pulses of radio frequency energy transmittedand reflected back to a sensor to detect respiration rate, heart rateand movement, etc. Alternatively, or in addition thereto, contactrespiratory monitoring devices such as a respiratory band or movementsensitive bed may be implemented to monitor patient respiratoryparameters.

The signals from the sensors may be sent to the controller 104. Optionalanalog-to-digital (A/D) converters/samplers (not shown separately) maybe utilized in the event that supplied signals from the sensors are notin digital form and the controller is a digital controller. Based on thesignals from the sensor(s), the controller assesses the condition of thepatient.

The controller may optionally include a display device 116 such as oneor more warning lights (e.g., one or more light emitting diodes). Thedisplay device may also be implemented as a display screen such as anLCD or a touch sensitive display. Activation of the display device 116will typically be set by the controller based on an assessment of thecondition by the apparatus 100. The display device may be implemented tovisually show information to a user of the apparatus 100 or a clinicianor physician. The display device 116 may also show a graphic userinterface for operation of the apparatus 100. User, clinician orphysician control of the operation of the apparatus 100 may be based onoperation of input switches 118 that may be sensed by the controller orprocessor of the apparatus.

Optionally, the controller may also include a communications device 120for receiving and/or transmitting data or messages by the apparatus 100.For example, the communications device may be a wireless transceiversuch as Bluetooth or WIFI transceiver. The communications device mayalso be a network communications device such as a phone modem and/ornetwork card and may be implemented to send messages via the internetdirectly or through a computer to which the detection device may bedocked. The communications device 120 may communicate with a remotedevice 122.

The controller 104 or processor 114 will typically be configured toimplement one or more particular control methodologies such as thealgorithms described in more detail herein. Thus, the controller mayinclude integrated chips, a memory and/or other control instruction,data or information storage medium. For example, programmed instructionsencompassing such a control methodology may be coded on integrated chipsin the memory of the device. Such instructions may also or alternativelybe loaded as software or firmware using an appropriate data storagemedium. In still further forms, control over parameters of treatment maybe set in accordance with a patient synchronization demand so as topermit a suitable treatment for mobility or exercise.

Some forms of the present technology involve an apparatus to generatepressure support ventilation. The apparatus may include at least onesensor adapted to measure at least one respiratory parameter and a flowgenerator adapted for coupling with a patient respiratory interface. Theflow generator may be configured to provide a flow of breathable gas forpressure support ventilation to the patient respiratory interface. Theapparatus may also include a controller coupled to the at least onesensor and the flow generator. The controller may be configured tocontrol the pressure support ventilation with the flow generator. Thecontroller may also be further configured with a rest mode and anexercise mode, the rest mode having a first value set of controlparameters for the pressure support ventilation and the exercise modehaving a second value set of control parameters for the pressure supportventilation.

In some cases, the controller may be configured to receive a useractivated trigger stimulus, and, in response to the trigger stimulus toselect the second value set of control parameters for the exercise mode.In response to the trigger stimulus, the controller may set a targetrespiratory control parameter as a function of a presently detectedrespiratory parameter sensed with the sensor. The target respiratorycontrol parameter may be a target respiratory rate and the detectedrespiratory parameter may be a measured respiratory rate. The targetrespiratory control parameter may be a target ventilation and thedetected respiratory parameter may be a measure of ventilation.Optionally, the target ventilation may be a target tidal volume and themeasure of ventilation may be a measure of tidal volume. Still further,the target ventilation may be a target minute ventilation and themeasure of ventilation may be a measure of minute ventilation. In somecases, the second value set of control parameters may comprise anincrease in target values with respect to the first value set of controlparameters.

Optionally, the apparatus may further include at least one useraccessible button to activate the controller such that the button may beconfigured for actuating the trigger stimulus. Still further, theapparatus may also include a diaphragm electromyogram sensor to activatethe controller such that the sensor may be configured for actuating thetrigger stimulus. In some cases, the apparatus may include a vagal nervesensor to activate the controller such that the sensor may be configuredfor actuating the trigger stimulus.

In some cases, the controller of the apparatus may be further configuredwith a cool down mode, and configured to receive another user activatedtrigger stimulus to initiate the cool down mode. The cool down mode mayinclude a third value set of control parameters for the pressure supportventilation. The controller may be configured such that a value of thecontrol parameters of the cool down mode may be varied from a respectivevalue of the control parameters of the exercise mode toward a respectivevalue of the control parameters of the rest mode. The controller may beconfigured such that a value of the control parameters of the cool downmode may be ramped from a respective value of the control parameters ofthe exercise mode toward a respective value of the control parameters ofthe rest mode.

Some forms of the present technology may involve a method for control ofpressure support ventilation. The method may include measuring at leastone respiratory parameter with a sensor. It may also include generatingpressure support ventilation with a flow generator adapted for couplingwith a patient respiratory interface. It may further includecontrolling, with a processor, the pressure support ventilation in arest mode and an exercise mode. The rest mode may have a first value setof control parameters for controlling the pressure support ventilationand the exercise mode may have a second value set of control parametersfor controlling the pressure support ventilation.

The method may further include receiving a user activated triggerstimulus, and, in response to the trigger stimulus, selecting the secondvalue set of control parameters for the exercise mode. The method mayalso include, in response to the trigger stimulus, setting a targetrespiratory control parameter as a function of a presently detectedrespiratory parameter sensed with the sensor. The target respiratorycontrol parameter may be a target respiratory rate and the detectedrespiratory parameter may be a measured respiratory rate. The targetrespiratory control parameter may be a target ventilation and thedetected respiratory parameter may be a measure of ventilation. Thetarget ventilation may be a target tidal volume and the measure ofventilation may be a measure of tidal volume. The target ventilation maybe a target minute ventilation and the measure of ventilation may be ameasure of minute ventilation. The second set of control parameters mayinclude an increase in target values with respect to the first value setof control parameters. In some such methods, a user accessible buttonactuates the trigger stimulus. In some such methods, a diaphragmelectromyogram sensor actuates the trigger stimulus. Still further, insome such methods, a vagal nerve sensor actuates the trigger stimulus.

Optionally, the methods may also include controlling pressure supportventilation in a cool down mode in response to receiving another useractivated trigger stimulus, the cool down mode may have a third valueset of control parameters for the pressure support ventilation. In somecases, a value of the control parameters of the cool down mode may bevaried from a respective value of the control parameters of the exercisemode toward a respective value of the control parameters of the restmode. In some cases, a value of the control parameters of the cool downmode may be ramped from a respective value of the control parameters ofthe exercise mode toward a respective value of the control parameters ofthe rest mode.

In some forms, the apparatus 100, such as when implemented to provide apressure treatment to patient suffering respiratory insufficiency, COPDor other similar ailments, may serve to enhance physical activity ormobility for a patient. For example, the apparatus may be implemented toprovide non-invasive ventilation to provide respiratory support forpatients during mobility. Such a non-invasive ventilation may enhanceexercise capacity in COPD patients or emphysemic patients. Thus, in someforms, a pressure treatment methodology, such as a control algorithm fornon-invasive pressure support ventilation, may be implemented to promoteexercise or patient mobility with suitable pressure support modes.

As a COPD patient gradually, exercises, their tidal volume andrespiratory rate will increase. When the patient then rests, the tidalvolume and respiratory rate decreases. In some forms of the presenttechnology, a patient-responsive non-invasive ventilation methodology ofthe apparatus may be configured to adapt to patients' varyingrespiratory needs during exertion or exercise.

Accordingly, FIG. 11 illustrates an example of a methodology of acontroller for such an apparatus. During use, the controller willgenerally permit a change to pressure support control parameters, suchas an increase in ventilation (e.g., tidal volume) and respiratory rateat levels, that are suitable for exercise or mobility up to a maximumventilation, such as a minute ventilation, and/or maxium respiratoryrate so as to provide pressure support at those levels. In order toachieve the desired levels, the apparatus may be configured to respondto a user or patient stimulus for setting the synchronization of theapparatus with the patient's exercise requirements.

For example, the apparatus may provide NIV at initial levels in a restmode to provide a pressure support suitable for a patient at rest at400. Thus, the apparatus may begin treatment by accessing stored valuesof target parameters for the rest mode where those values of the targetparameters are suitable for controlling ventilation or pressure supportfor patient rest. The user or patient may then begin to exercise. Duringexercise or shortly before, the patient may then provide a stimulus,such as executing a trigger, to initiate a modification procedure of theapparatus so that the apparatus may begin an exercise mode at 401. Themodification procedure permits the values of the target parameters ofthe pressure support to be modified or set such that the pressuresupport will be provided at more suitable levels (e.g., increases intarget ventilation (e.g., minute ventilation or tidal volume) or intarget respiratory rate, or in the maximum or minimum values suitablefor controlling pressure support) for exercise at 402. Thus, themodification procedure of the exercise mode may allow enforcement ofdifferent minimum and/or maximum values and/or target values ofrespiratory control parameters in the exercise mode at 403 from the restmode.

In some such forms, the triggered change or, increase to the values ofthe control parameters of the pressure support ventilation for theexercise mode may optionally be predetermined. In such a case, theexecuted trigger may result in the apparatus accessing one or morestored values for the control parameters for the pressure support wherethe stored values of the control parameters are associated with theexercise mode. Such target, minimum and/or maximum values may bepreviously entered by a physician or clinician. For example, arespiratory rate target or ventilation target may be set as a physicianselectable proportional function of the values of the control parametersof the rest mode so as to permit a proportional increase (or decrease)of the parameters from the rest mode. Optionally, in some forms, some ofthe values of the control parameters of the pressure support ventilationof the exercise mode may be learned so as to better synchronize with thelevel exercise of the user or patient. For example, the apparatus maylearn the exercise respiratory rate, minute ventilation and/or tidalvolume of the patient during an initial exercise period of the exercisemode or in response to a stimulus signal of the patient, such as bymeasuring these parameters from a flow signal in the initial period.Thereafter, such learned values may then be set for the controlparameters of a later time period of the exercise mode.

In some forms, the stimulus for entering the exercise mode or making anadjustment to target values to accommodate the patient's state ofexercise may be made by the patient by pressing a button of thetreatment apparatus or a button on a remote control (e.g., a wired,wireless or infrared transmitter to transmit to an exercise mode signalor exercise synchronization signal to a receiver of the apparatus).Alternatively, the stimulus signal may be a detected physiologicalstimulus such as for example, a signal from a diaphragm electromyogramsensor, a signal from a sensor that is responsive to activation of thevagal nerve e.g. an oximeter, or an evaluation of a signal from a flowsensor.

In some forms, as further illustrated in FIG. 11, the apparatus may beconfigured to receive additional stimulus signals or executed triggersfrom the patient as the exercise progresses or cools down in or from theexercise mode. For example, with each additional stimulus signal, a newset of control values may be established. For example, at 404 a patientor user may trigger learning or loading of a further set of values forthe control parameters. The new targets may then be set as the controlparameters for the delivery of the pressure support ventilation at 405.The apparatus 100 may then control the pressure support in accordancewith the new settings at 403. Each set of control values may be higheror lower than the previous control values based on an increase ordecrease of activity.

For example, in some forms, the exercise mode may have a predeterminedtime interval, such as a maximum time set by a physician or clinician.In some such forms, a timer may begin when the exercise mode starts andthe mode may terminate when a preset maximum time is reached. During theexercise mode, the apparatus may deliver pressure support ventilationwith the exercise mode control values that are suitable for patientexercise. At the conclusion of the exercise mode, the apparatus mayswitch to the rest mode, so as to deliver pressure support ventilationwith the rest mode control values that are suitable for patient rest.Optionally, the apparatus or remote control may include a button toterminate the exercise mode before the maximum time is reached.

Still further, in some forms, the termination of the exercise mode mayinitiate a cool down mode. During the cool down mode, the values of thecontrol parameters may be varied over a selectable period of time. Forexample, the values may be ramped from the values of the targetparameters of the exercise mode to the values of the target parametersof the rest mode. For example, the respiratory rate and/or ventilationtargets may be automatically modified so as to ramp down or be graduallystepped down over a period of time to the rest mode values.

5.4 OTHER ASPECTS

The present technology may be packaged as an exercise module oraccessory to be used with a range of different ventilators.

Preferably the parameters that are adjustable by the patient areadjustable within limits. Such limits may be established by a clinicianprior to use by the patient.

5.5 ADVANTAGES

One advantage of the present technology is that it allows ventilators tomore closely match a patient's need, particularly in the face of achanging need, e.g. increasing or decreasing, such as when a patientattempts to exercise.

An advantage of the present technology is that it is easier and morecomfortable for patients to use when compared to a ventilator that mayhave one fixed setting of e.g. minute ventilation, or pressure support.

In addition, the present technology allows a patient to pre-empt a needfor a sooner breath, or an increased level of support. By pressing onthe relevant button momentarily before they require a breath, the systemcan respond just as the patient actually needs the breath.

5.6 REFERENCE SIGNS LIST

-   apparatus 10-   ventilator 12-   button 14-   pc 16-   digital communication interface 18-   inflection point 17-   pressure support 19-   Pathway 21-   Apparatus 100-   Patient respiratory interface 102-   Controller 104-   Blower 105-   Pressure sensor 106-   Flow sensor 107-   Mask 108-   Delivery tube 110-   Additional diagnosis sensors 112-   Processor 114-   Display device 116-   Input switches 118-   Communications device 120-   Remote device 122-   Patient interface 3000-   pap device 4000-   external housing 4010-   panel 4015-   chassis 4016-   handle 4018-   pneumatic block 4020-   pneumatic component 4100-   inlet air filter 4112-   blower 4142-   pressure sensor 4152-   flow sensor 4154-   Air circuit 4170-   electrical component 4200-   PCBA 4202-   power supply 4210-   input device 4220-   processor 4230-   clock 4232-   pressure device controller 4240-   protection circuit 4250-   memory 4260-   transducer 4270-   flow transducer 4271-   pressure transducer 4272-   Oximeter 4273-   Electromyograph 4274-   output device 4290-   algorithm 4300-   humidifier 5000

5.7 OTHER REMARKS

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being preferably used toconstruct a component, obvious alternative materials with similarproperties may be used as a substitute.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated by reference todisclose and describe the methods and/or materials which are the subjectof those publications. The publications discussed herein are providedsolely for their disclosure prior to the filing date of the presentapplication. Nothing herein is to be construed as an admission that thepresent technology is not entitled to antedate such publication byvirtue of prior invention. Further, the dates of publication providedmay be different from the actual publication dates, which may need to beindependently confirmed.

Moreover, in interpreting the disclosure, all terms should beinterpreted in the broadest reasonable manner consistent with thecontext. In particular, the terms “comprises” and “comprising” should beinterpreted as referring to elements, components, or steps in anon-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

It is therefore to be understood that numerous modifications may be madeto the illustrative embodiments and that other arrangements may bedevised without departing from the spirit and scope of the technology.

The invention claimed is:
 1. A controller for a ventilator, theventilator being configured to deliver a pressure support waveform to apatient, said pressure support waveform having an inspiratory phase anda subsequent expiratory phase, and the controller being configured toadjust an expiratory pressure during the expiratory phase in response toan indication of a change in metabolic demand of the patient, whereinthe controller is configured so that in response to an increase in alevel of metabolic demand up to a predetermined limit of metabolicdemand, the controller increases a level of the expiratory pressure to alevel no higher than a maximum expiratory pressure value, and whereinthe controller is further configured so that in response to an increasein the level of metabolic demand above the predetermined limit ofmetabolic demand, the controller increases a level of inspiratorypositive pressure while a level of expiratory positive air pressure willremain substantially constant at the maximum expiratory pressure value.2. The controller of claim 1, wherein the controller is furtherconfigured to accept a signal from a metabolic demand responsivetransducer, and to determine a state of metabolic demand from saidmetabolic demand responsive transducer.
 3. The controller of claim 2,wherein said metabolic demand responsive transducer is an oximeter. 4.The controller of claim 2, wherein said metabolic demand responsivetransducer is a flow sensor.
 5. The controller of claim 2, wherein saidmetabolic demand responsive transducer is a diaphragm electromyograph.6. The controller of claim 2, wherein said metabolic demand responsivetransducer is a combination of a flow sensor and an electromyograph. 7.The controller of claim 1, configured to increase an inspiratorypressure at a first rate in response to an increase in metabolic demandup to a given point.
 8. The controller of claim 7, configured toincrease an inspiratory pressure at a second rate in response to anincrease in metabolic demand above the given point.
 9. The controller ofclaim 8 wherein the second rate is lower than the first rate.
 10. Thecontroller of claim 1 wherein a maximum expiratory pressure value at thegiven point is about 10 cmH₂0.
 11. The controller of claim 1 configuredto follow a predetermined pressure support pathway.
 12. The controllerof claim 1, wherein at least for a range of metabolic demand values, thecontroller is configured to linearly adjust the at least one parameterof the ventilator in response to a change in metabolic demand values inthe range.
 13. The controller of claim 1, wherein at least for a rangeof metabolic demand values, the controller is configured to discretelyadjust between metabolic demand values in the range.
 14. The controllerof claim 1, wherein the indication of change in metabolic demand isinput manually.
 15. The controller of claim 1, wherein the indication ofchange in of metabolic demand is determined automatically.
 16. Aventilator for providing ventilatory support to a patient, theventilator comprising: a power supply; a controller as claimed in claim1; and a pressure device under the control of the controller. 17.Apparatus for providing ventilatory assistance to a patient to assist inexercising comprising a ventilator as claimed in claim 16, and ametabolic demand responsive transducer.
 18. A controller for aventilator, the ventilator being configured to deliver a pressuresupport waveform to a patient, said pressure support waveform having aninspiratory phase and a subsequent expiratory phase, and the controllerbeing configured to adjust an expiratory pressure during the expiratoryphase in response to an indication of a change in metabolic demand ofthe patient, wherein the controller is configured so that in response toan increase in a level of metabolic demand up to a first metabolicdemand threshold, the controller increases a level of the expiratorypressure to a level no higher than a maximum expiratory pressure value,and wherein the controller is further configured so that in response toan increase in the level of metabolic demand above the first metabolicdemand threshold, the controller increases a level of inspiratorypositive pressure while a level of expiratory positive air pressure willremain substantially at the maximum expiratory pressure value.
 19. Amethod of control of a ventilator, the ventilator being configured todeliver a pressure support waveform to a patient, said pressure supportwaveform having an inspiratory phase and a subsequent expiratory phase,the method comprising: adjusting with a processor an expiratory pressureduring the expiratory phase in response to an indication of a change inmetabolic demand of the patient, so that in response to an increase in alevel of metabolic demand up to a predetermined limit of metabolicdemand, a level of the expiratory pressure increases to a level nohigher than a maximum expiratory pressure value, and so that in responseto an increase in the level of metabolic demand above the predeterminedlimit of metabolic demand, a level of inspiratory positive pressureincreases while a level of expiratory positive air pressure will remainsubstantially constant at the maximum expiratory pressure value.
 20. Themethod of claim 19, further comprising with the processor, accepting asignal from a metabolic demand responsive transducer and determining astate of metabolic demand from said metabolic demand responsivetransducer.
 21. The method of claim 20, wherein said metabolic demandresponsive transducer is an oximeter.
 22. The method of claim 20,wherein said metabolic demand responsive transducer is a flow sensor.23. The method of claim 20, wherein said metabolic demand responsivetransducer is a diaphragm electromyograph.
 24. The method of claim 20,wherein said metabolic demand responsive transducer is a combination ofa flow sensor and an electromyograph.
 25. The method of claim 19,further comprising with the processor increasing an inspiratory pressureat a first rate in response to an increase in metabolic demand up to agiven point.
 26. The method of claim 25, further comprising with theprocessor increasing an inspiratory pressure at a second rate inresponse to an increase in metabolic demand above the given point. 27.The method of claim 26 wherein the second rate is lower than the firstrate.
 28. The method of claim 19 wherein a maximum expiratory pressurevalue at the given point is about 10 cmH₂0.
 29. The method of claim 19further comprising with the processor following a predetermined pressuresupport pathway.
 30. The method of claim 19, wherein at least for arange of metabolic demand values, linearly adjusting with the processorthe at least one parameter of the ventilator in response to a change inmetabolic demand values in the range.
 31. The method of claim 19,wherein at least for a range of metabolic demand values, discretelyadjusting with the processor between metabolic demand values in therange.
 32. The method of claim 19, wherein the indication of change inmetabolic demand is input manually to the processor.
 33. The method ofclaim 19, wherein the indication of change in metabolic demand isdetermined automatically by the processor.